These studies are a continuation of an indepth investigation into the thymus-derived lymphocyte (T cell), its antigen receptor, and its products. Continuously propagable cloned T cell lines have been established in the course of this work by hybridizing murine antigen specific cells with BW 5147, a T lymphoma. Clones have been identified which express antigen specificity in two of the hybrid series. One reacts with ovalbumin, one group reacts with azobenzenearsonate. Molecular characterization of the secreted products and membrane proteins will be done. These studies should permit isolation and characterization of the T cell receptor for antigen.